1. Field of the Invention
The present invention relates to a switching system for switching, for instance, one computer operated in an on-line condition and the other computer having the same performance as that of one computer, set on standby for back-up purposes.
2. Description of the Related Art
The switching system described in the preamble is known from, for instance, Japanese KOKAI (Disclosure) Utility Model Application No. 63-159436 opened on Oct. 19, 1988.
In FIG. 1, there is shown another conventional switching system. As represented in FIG. 1, this switching system is constructed of two computers 2 and 3 which are selectively, operable under an on-line condition and also on standby for back-up purposes, and a switching controller 1 for furnishing a condition-switching instruction to these computers 2 and 3, respectively.
The switching controller 1 is connected via connectors 8A, 8B, 13A, 13B and signal lines 9A, 9B, 10A, 10B to the computers 2 and 3. From the switching controller 1, on-line/standby condition switching signals 11A and 11B, and also normal/malfunction condition signals 12A and 12B are supplied via these corresponding signal lines 9A, 9B, 10A and 10B, so that, for instance, the first computer 2 is set to the on-line condition, whereas the second computer 3 is set to the standby condition at the same time.
The above-described conventional switching system has the following problems. That is, in addition to the originally required on-line/standby condition switching signals 11A and 11B, both the normal/malfunction condition signals 12A and 12B must be sent from the switching controller 1 to the respective computers 2 and 3 in order to confirm malfunction of the switching controller 1 and a disconnection of the connectors 8A, 8B, 13A and 13B. To this end, as shown in FIG. 1 , an extra circuit is necessarily required in the switching controller 1. Furthermore, it cannot be guaranteed that the computers 2 and 3 are simultaneously controlled in case of, e.g., a malfunction with the circuit arrangement shown in FIG. 1.